Many herbicides injure crop plants at herbicide application rates necessary to control weed growth. Accordingly, many herbicides cannot be used for controlling weeds in the presence of certain crops. Uncontrolled weed growth, however, results in lower crop yield and reduced crop quality inasmuch as weeds compete with crops for light, water and soil nutrients. Reduction of herbicidal injury to crops without an unacceptable corresponding reduction of herbicidal action on the weeds can be accomplished by use of crop protectants known as herbicide "antagonists", "antidotes" or "safeners".
Weed control for crops, especially corn crops, is one of the oldest and most highly developed areas in weed science. For a herbicide product to be accepted commercially for corn crops, such herbicide product must provide a relatively high level of control of both grassy and broadleaf weeds in corn, in addition to meeting several other criteria. For example, the herbicide should possess relatively high unit activity so that lower rates of herbicide application are feasible. Lower application rates are desirable in order to minimize exposure of the environment to the herbicide. At the same time, such herbicide must be selective in herbicidal effect so as not to injure the crops. Herbicidal selectivity can be enhanced by use of an appropriate antidote in combination with the herbicide. But identification of an antidote which safens a herbicide or mixture of herbicides in crops is a highly complicated task. Whether a compound or class of compounds provides efficacious antidote or safening activity is not a theoretical determination but must be done empirically. Safening activity is determined empirically by observing the complex interaction of several biological and chemical factors, namely: the type of herbicide compound; the type of weed to be controlled; the type of crop to be protected from weed competition and herbicidal injury; and the antidote compound itself. Moreover, the herbicide and antidote must each possess chemical and physical properties enabling preparation of a stable formulation which is environmentally safe and easy to apply to the field.
Among the various classes of compounds found to be suitable for various herbicidal purposes are the .alpha.-haloacetanilides and sulfonylureas. The former herbicides in commercial embodiments include, e.g., alachlor, acetochlor, metolachlor, etc., are excellent preemergence or early post emergence herbicides for controlling annual grasses and many broadleaved weeds in corn, peanuts, soybeans and other crops, while some of the latter herbicides, exemplified by chlorsulfuron, thifensulfuron methyl, chlorimuron ethyl, triasulfuron, metsulfuron methyl, bensulfuron methyl and the like, may be used as a foliar- or soil-applied herbicide suitable for the control of many annual and perennial broadleaved species in asparagus, cereals, corn, grain sorghum, sugarcane, soybean and other crops and woody brush and vine control in pasture, rangeland and cropland. Other sulfonylureas can be used in preplant or preemergence applications.
It is a common agronomic practice to use various antidotal compounds to reduce the phytotoxicity of some herbicides to various crops. For example, flurazole (active ingredient in SCREEN.RTM. safener) is used as a seed dressing to protect sorghum seed from alachlor (active ingredient in LASSO.RTM. herbicide). Similarly, cyometrinil (active ingredient in CONCEP.RTM. safener) has been used as a grain sorghum seed safener for use with metolachlor and oxabetrinil (active ingredient in CONCEPII.RTM. safener) is also used to safen sorghum seed from injury by metolachlor. Cyometrinil is also described in U.S. Pat. No. 4,070,389 as an antidote against chloroacetanilide and thiocarbamate herbicides in millet and rice. The compound N,N-diallyl dichloroacetamide (common name "dichlormid"; code number R-25788) is used to safen corn from injury by the thiocarbamate 5-ethyl-N,N-dipropylthiocarbamate (active ingredient in ERADICANE.RTM. herbicide) and by acetochlor (active ingredient in WENNER.RTM. herbicides). The antidotal compound "AD-67" is used to safen corn from injury by acetochlor in the commercial herbicides GUARDIAN.RTM. and ACENIT.RTM..
It is also disclosed in the literature to use the safener fenchlorim to safen the .alpha.-chloroacetanilide herbicide pretilachlor alone or in the presence of a sulfonylurea having the common name "cinosulfuron" (active ingredient in SOFIT.RTM. SUPER herbicide). Fenchlorim and cinosulfuron are identified by chemical name infra. Cinosulfuron is characterized by substituted-phenylsulfonyl- and substituted-triazinyl radicals on the respective urea nitrogen atoms. It is also known to use a variety of safeners to safen the sulfonylurea having the common name "primisulfuron" (active ingredient in BEACON.RTM. herbicide). Primisulfuron is characterized by substituted-phenylsulfonyl- and substituted-pyrimidinyl radicals on the respective urea nitrogen atoms; its chemical structure is identified below.
It has also been disclosed in the prior art to use 1,8-naphthalic anhydride, R-25788 and cyometrinil to safen cereal crops, e.g., corn, wheat, rice and sorghum against certain sulfonylureas characterized by substituted-phenylsulfonyl- and either substituted-pyrimidinyl- or -triazinyl radicals on the respective urea nitrogen atoms (U.S. Pat. No. 4,343,649). Another reference (EP Application No. 147365, published Jul. 3, 1985) also discloses the safening of a class of sulfonylureas similar to those in said U.S. '649 patent with the same safeners and two additional ones, i.e., R-28725 and flurazole; the chemical identities of the safeners disclosed in these two references is described below.
Applicant's assignee has published patent applications relating to the use of various 5-heterocyclic-substituted oxazolidine dichloroacetamide safeners for use with a variety of herbicides including .alpha.-chloroacetanilides and sulfonylureas and mixtures thereof.
Prior to my discovery detailed herein it was not known to my knowledge to safen pyrazolylsulfonylurea herbicides, although such herbicides, per se, were known, e.g., from U.S. Pat. Nos. 4,668,277 and 4,931,081 and EP Application Publication Nos. 282,613 (Sep. 21, 1988), 087,780 (Aug. 18, 1982) and South African Published Application 83/03850 (Nov. 28, 1983).
It is an object of this invention to provide compositions of pyrazolylsulfonylureas in combination with antidotes therefor, optionally containing a coherbicide, which compositions are useful to reduce injury to crops, especially corn, due to phytotoxicity of said herbicides.